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Butter Pats and Battleships

Reader Devin wants to know why you mix a little bit of flour into the butter pat when you’re making laminated dough. What purpose does it serve? For the answer to that, Devin, we’re going to journey back to World War II and the allied war effort.

The year was 1942. The British were fighting the good fight against the Axis powers, but still losing too many ships in the English Channel and too many American supply convoys in the Atlantic. What was needed was air cover. The problem was that the fighters and torpedo planes of the day couldn’t fly very far on the fuel they carried, which meant they could only go so far out to sea before they were forced to turn back and head for home. That left the merchant marines at the mercy of U-boat wolf packs for most of their journey across the Atlantic. The obvious solution: aircraft carriers. They’d be able to sit out in the ocean and refuel planes as they crossed the pond from east to west and back again. The fly in the ointment was that aircraft carriers were (are) made of steel, and steel was in very short supply just then.

Enter an ingenious — if very odd and cantankerous — inventor by the name of Geoffrey Pyke. Pyke dreamt up a daring solution to the carrier problem: land the planes on icebergs instead. They could be cut from the Arctic ice sheet and towed to where they were needed. The was just one problem: icebergs were well known for being of highly variable thickness, so they were prone to flipping over when you least expected it. Pyke’s solution: create man-made ice aircraft carriers out of industrially-made ice. The idea’s so crazy it just might work! Or so thought Pyke’s greatest patron in the British armed forces, one Lord Mountbatten.

And so development began in Canada, where engineers started to work on the problem of the base material: ice. They realized that while ice is hard and it floats, it’s also very brittle. Could it be improved in any way? As it happened, it could. By mixing the water with about 15% sawdust and freezing it they created a remarkable ice-wood hybrid, one with over double the crushing strength of regular ice and quintuple the tensile strength — and that could be shaped and planed almost exactly like wood. Functionally the stuff was strong as steel — but light and buoyant — and could be produced for about 1% the cost. A true miracle material it was. Pyke’s team christened it “pykrete” in his honor.

But hang on, there was one problem: wound’t pykrete melt? Well, yes, but only very slowly because the wood pulp had the effect of insulating the water crystals against outside heat. Run some refrigerated air through ducts embedded in the hull of the ship to keep the pykrete cool and…problem solved. Pyke began to design behemoth vessels, bigger than any ships ever conceived, capable of landing and launching planes of any size and carrying almost inexhaustible supplies of fuel and munitions. Presented with the plan, Winston Churchill signed onto the initiative, codenamed “Project Habakkuk.”

Of course not everyone loved the idea. Habakkuk was derided by many leading lights in the British navy who complained that the ice ship’s top speed of between 4 and 8 miles an hour made it impractical for sneaking up on the enemy. Pyke countered that when you have a mobile, unsinkable, 4,000-foot-long, 700-foot-wide, 4-million-ton battle platform you don’t need to sneak up anyone again, ever. The admiralty conceded that Pyke had a point, especially considering that a pykrete carrier would (at least in theory) be bomb, bullet and torpedo-proof, as well as capable of housing and launching heavy bombers by the dozens and Spitfires by the hundreds.

So what happened? Why were no pykrete ships — outside of a 60-foot prototype launched on Patricia Lake in Canada — ever launched? For several reasons. Technical problems like steering and refrigeration were some of them. Also the inconvenient fact that even though the ship was made of ice, you still needed steel to make the freezers that made the ice. About as much as you’d need to build a whole aircraft carrier. Add to all this that by 1943, just as some of Project Habakkuk’s initial successes were being realized, advances in technology were giving airplanes like the B-24 Liberator greater range. New planes equipped with radar and depth charges were devastating the wolf packs. The Battle of the Atlantic was being won. Which meant there was no longer a need for pykrete ships. Oh well.

All of which has what to do with flour and butter pats, exactly? I forget, other than something about not underestimating the ability of a small proportion of particulates to insulate a much larger volume of melt-able matter.